Error message in update manager (new user)

Help would be appreciated with updates for Hardy Heron 8.0.4.1. I was "trying" to follow the comprehensive multimedia & video how to and admit that I lost the plot. I now get error messages on update manager. I don't know how to undo anything wrong that I may have done. Should I go back to a fresh install or something? It's fun experimenting but I'm running into walls everywhere I go. I tried a screne shot of the error and will try to attach it here. Thanks, Tim